1. Field of the Invention
The present invention relates to a fuel cell including an electrolyte electrode assembly, and separators for sandwiching the electrolyte electrode assembly. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes. In the fuel cell, reactant gas flow fields are formed on surfaces of the separators for supplying reactant gases along the surfaces of the separators. Each of the reactant gas flow fields is connected between a reactant gas supply passage and a reactant gas discharge passage.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a membrane electrode assembly (MEA) which includes two electrodes (anode and cathode), and an electrolyte membrane interposed between the electrodes. The electrolyte membrane is a polymer ion exchange membrane. The membrane electrode assembly is interposed between separators.
In the fuel cell, a fuel gas (reactant gas) such as a gas chiefly containing hydrogen (hydrogen-containing gas) is supplied to the anode. The catalyst of the anode induces a chemical reaction of the fuel gas to split the hydrogen molecule into hydrogen ions (protons) and electrons. The hydrogen ions move toward the cathode through the electrolyte, and the electrons flow through an external circuit to the cathode, creating a DC electric current. A gas chiefly containing oxygen (oxygen-containing gas) or air is supplied to the cathode. At the cathode, the hydrogen ions from the anode combine with the electrons and oxygen to produce water.
In the fuel cell, the fuel gas, the oxygen-containing gas, and the coolant flow through their dedicated fluid passages which are hermetically sealed for preventing gas or liquid leakages. Typically, seal members are interposed between the membrane electrode assembly and the separator for preventing leakages. Various types of seal members are known. For example, U.S. Pat. No. 5,284,718 discloses a seal structure shown in FIG. 10. According to the disclosure, a membrane electrode assembly (membrane electrode and seal assembly) comprises a porous electrically conductive sheet material 1.
The electrically conductive sheet material 1 has an air inlet opening 2a and an air outlet opening 2b at one corner, and a hydrogen inlet opening 3a and a hydrogen outlet opening 3b at another corner. Further, a coolant inlet opening 4a and a coolant outlet opening 4b are formed at a corner diagonally opposite to the corner of the hydrogen inlet opening 3a and the hydrogen outlet opening 3b. A solid gasket 5 is provided in the electrically conductive sheet material 1. The gasket 5 is placed in a channel 6 when the fuel cell stack is assembled.
The gasket 5 includes seal members 5a provided around the outer area of the electrically conductive sheet material 1. The seal members 5a are connected to the seal members 5b. Thus, seal joints 5c for connecting the seal members 5a, 5b are provided on the seal surface of the gasket 5.
According to the structure, however, the adjacent seal members 5a, 5b are likely to be affected by each other. Specifically, local line pressure or surface pressure applied to the seal joint 5a increases excessively. Consequently, the electrically conductive sheet material 1 may be deformed undesirably, and the desired sealing performance can not be achieved.